1. Technical Field
The present invention relates to a run flat tire.
2. Related Art
There is a pneumatic tire called a run flat tire that can run in a certain extent of distance even in the state that air pressure in a tire has reduced and reached 0 kPa by tire failure such as puncture. It is known to reinforce a side wall part by providing a side reinforcing rubber part on an inner surface of the side wall part as a technique for enabling run flat running in the state that an inner pressure has reduced as above.
High hardness compounded rubber composition is frequently used in a side reinforcing rubber part to suppress deformation of a tire during run flat running (for example, JP-A-2007-070373 and JP-A-2010-149632). However, a temperature of a side reinforcing rubber part is increased during run flat running, and as a result, rigidity of the side reinforcing rubber part is decreased, resulting in decrease of run flat durability.
JP-A-2008-189911 discloses that a rubber composition having a phenol type thermosetting resin and a methylene donor added thereto is used in a side reinforcing rubber part of a run flat tire. However, this literature does not disclose that rigidity of a rubber that is generally decreased at high temperature is set to rigidity equal to or more than that at ordinary temperature in order to improve run flat durability. Furthermore, this literature does not disclose that a quinoline type age resister is used together with the phenol type thermosetting resin and the methylene donor.
JP-A-2011-190410 discloses that in the technology of adding zinc oxide and aluminum nitride to a rubber composition for a run flat tire, a quinoline type age resister is added as an age resister. However, this literature does not disclose that rigidity of a rubber at high temperature is set to rigidity equal to or more than that at ordinary temperature in order to improve run flat durability. Furthermore, this literature does not disclose that a phenol type thermosetting resin and a methylene donor are used together with the quinoline type age resister.